There haven't been many fantasy games that do away with medieval knights slaying dragons with swords in favor of WWI dough boys slaying them with tanks, artillery, and machine guns, have there?
It might be hard to imagine an RPG set in a world where goblins, bugbears, and necromancers seamlessly coexist with guns, electric appliances, and boomboxes but can anybody recall any games that attempt to create a fantasy world where Orcs have Kalashnikovs, wear sunglasses with puffer vests, and drink 40 ounces and get their kicks by mugging elves with briefcases and three piece suits?
How would a machine gun work in RPG's like D&D or Dragon Quest, anyway? It's not like your strength or dexterity stats would make a difference about how hard a bullet hits because that doesn't depend on how hard you pull the bolt on your Mauser.